<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>fc - Perldoc Browser</title>
    <link rel="search" href="https://perldoc.perl.org/opensearch.xml" type="application/opensearchdescription+xml" title="Perldoc Browser">
    <link rel="canonical" href="https://perldoc.perl.org/functions/fc">
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css" integrity="sha384-JcKb8q3iqJ61gNV9KGb8thSsNjpSL0n8PARn9HuZOnIxN0hoP+VmmDGMN5t9UJ0Z" crossorigin="anonymous">
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/10.5.0/styles/stackoverflow-light.min.css" integrity="sha512-cG1IdFxqipi3gqLmksLtuk13C+hBa57a6zpWxMeoY3Q9O6ooFxq50DayCdm0QrDgZjMUn23z/0PMZlgft7Yp5Q==" crossorigin="anonymous" />
    <style>
      body {
        background: #f4f4f5;
        color: #020202;
      }
      .navbar-dark {
        background-image: -webkit-linear-gradient(top, #005f85 0, #002e49 100%);
        background-image: -o-linear-gradient(top, #005f85 0, #002e49 100%);
        background-image: linear-gradient(to bottom, #005f85 0, #002e49 100%);
        filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#ff005f85', endColorstr='#ff002e49', GradientType=0);
        background-repeat: repeat-x;
      }
      .navbar-dark .navbar-nav .nav-link,
      .navbar-dark .navbar-nav .nav-link:focus { color: #fff }
      .navbar-dark .navbar-nav .nav-link:hover { color: #ffef68 }
      #wrapperlicious {
        margin: 0 auto;
        font: 0.9em 'Helvetica Neue', Helvetica, sans-serif;
        font-weight: normal;
        line-height: 1.5em;
        margin: 0;
        padding: 0;
      }
      #wrapperlicious h1 { font-size: 1.5em }
      #wrapperlicious h2 { font-size: 1.3em }
      #wrapperlicious h3 { font-size: 1.1em }
      #wrapperlicious h4 { font-size: 0.9em }
      #wrapperlicious h1, #wrapperlicious h2, #wrapperlicious h3,
      #wrapperlicious h4, #wrapperlicious dt {
        color: #020202;
        margin-top: 1em;
        margin-bottom: 1em;
        position: relative;
        font-weight: bold;
      }
      #wrapperlicious a { color: inherit; text-decoration: underline }
      #wrapperlicious #toc { text-decoration: none }
      #wrapperlicious a:hover { color: #2a2a2a }
      #wrapperlicious a img { border: 0 }
      #wrapperlicious :not(pre) > code {
        color: inherit;
        background-color: rgba(0, 0, 0, 0.04);
        border-radius: 3px;
        font: 0.9em Consolas, Menlo, Monaco, monospace;
        padding: 0.3em;
      }
      #wrapperlicious dd {
        margin: 0;
        margin-left: 2em;
      }
      #wrapperlicious dt {
        color: #2a2a2a;
        font-weight: bold;
        margin-left: 0.9em;
      }
      #wrapperlicious p {
        margin-bottom: 1em;
        margin-top: 1em;
      }
      #wrapperlicious li > p {
        margin-bottom: 0;
        margin-top: 0;
      }
      #wrapperlicious pre {
        border: 1px solid #c1c1c1;
        border-radius: 3px;
        font: 100% Consolas, Menlo, Monaco, monospace;
        margin-bottom: 1em;
        margin-top: 1em;
      }
      #wrapperlicious pre > code {
        display: block;
        background-color: #f6f6f6;
        font: 0.9em Consolas, Menlo, Monaco, monospace;
        line-height: 1.5em;
        text-align: left;
        white-space: pre;
        padding: 1em;
      }
      #wrapperlicious dl, #wrapperlicious ol, #wrapperlicious ul {
        margin-bottom: 1em;
        margin-top: 1em;
      }
      #wrapperlicious ul {
        list-style-type: square;
      }
      #wrapperlicious ul ul {
        margin-bottom: 0px;
        margin-top: 0px;
      }
      #footer {
        font-size: 0.8em;
        padding-top: 0.5em;
        text-align: center;
      }
      #more {
        display: inline;
        font-size: 0.8em;
      }
      #perldocdiv {
        background-color: #fff;
        border: 1px solid #c1c1c1;
        border-bottom-left-radius: 5px;
        border-bottom-right-radius: 5px;
        margin-left: auto;
        margin-right: auto;
        padding: 3em;
        padding-top: 1em;
        max-width: 960px;
      }
      #moduleversion { float: right }
      #wrapperlicious .leading-notice {
        font-style: italic;
        padding-left: 1em;
        margin-top: 1em;
        margin-bottom: 1em;
      }
      #wrapperlicious .permalink {
        display: none;
        left: -0.75em;
        position: absolute;
        padding-right: 0.25em;
        text-decoration: none;
      }
      #wrapperlicious h1:hover .permalink, #wrapperlicious h2:hover .permalink,
      #wrapperlicious h3:hover .permalink, #wrapperlicious h4:hover .permalink,
      #wrapperlicious dt:hover .permalink {
        display: block;
      }
    </style>
    <!-- Global site tag (gtag.js) - Google Analytics -->
    <script async src="https://www.googletagmanager.com/gtag/js?id=G-KVNWBNT5FB"></script>
    <script>
      window.dataLayer = window.dataLayer || [];
      function gtag(){dataLayer.push(arguments);}
      gtag('js', new Date());

      gtag('config', 'G-KVNWBNT5FB');
      gtag('config', 'UA-50555-3');
    </script>
  </head>
  <body>
    <nav class="navbar navbar-expand-md navbar-dark bg-dark justify-content-between">
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  </button>
  <a class="navbar-brand" href="https://perldoc.perl.org/">Perldoc Browser</a>
  <div class="collapse navbar-collapse" id="navbarNav">
    <ul class="navbar-nav mr-auto">
      <li class="nav-item dropdown text-nowrap">
        <a class="nav-link dropdown-toggle" href="fc.html#" id="dropdownlink-stable" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">5.35.0</a>
        <div class="dropdown-menu" aria-labelledby="dropdownlink-stable">
          <a class="dropdown-item" href="https://perldoc.perl.org/functions/fc">Latest</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.38.2/functions/fc">5.38.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.38.1/functions/fc">5.38.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.38.0/functions/fc">5.38.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.36.3/functions/fc">5.36.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.36.2/functions/fc">5.36.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.36.1/functions/fc">5.36.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.36.0/functions/fc">5.36.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.34.3/functions/fc">5.34.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.34.2/functions/fc">5.34.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.34.1/functions/fc">5.34.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.34.0/functions/fc">5.34.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.32.1/functions/fc">5.32.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.32.0/functions/fc">5.32.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.30.3/functions/fc">5.30.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.30.2/functions/fc">5.30.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.30.1/functions/fc">5.30.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.30.0/functions/fc">5.30.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.28.3/functions/fc">5.28.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.28.2/functions/fc">5.28.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.28.1/functions/fc">5.28.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.28.0/functions/fc">5.28.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.26.3/functions/fc">5.26.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.26.2/functions/fc">5.26.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.26.1/functions/fc">5.26.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.26.0/functions/fc">5.26.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.24.4/functions/fc">5.24.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.24.3/functions/fc">5.24.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.24.2/functions/fc">5.24.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.24.1/functions/fc">5.24.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.24.0/functions/fc">5.24.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.22.4/functions/fc">5.22.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.22.3/functions/fc">5.22.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.22.2/functions/fc">5.22.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.22.1/functions/fc">5.22.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.22.0/functions/fc">5.22.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.20.3/functions/fc">5.20.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.20.2/functions/fc">5.20.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.20.1/functions/fc">5.20.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.20.0/functions/fc">5.20.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.18.4/functions/fc">5.18.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.18.3/functions/fc">5.18.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.18.2/functions/fc">5.18.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.18.1/functions/fc">5.18.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.18.0/functions/fc">5.18.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.16.3/functions/fc">5.16.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.16.2/functions/fc">5.16.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.16.1/functions/fc">5.16.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.16.0/functions/fc">5.16.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.14.4/functions/fc">5.14.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.14.3/functions/fc">5.14.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.14.2/functions/fc">5.14.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.14.1/functions/fc">5.14.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.14.0/functions/fc">5.14.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.12.5/functions/fc">5.12.5</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.12.4/functions/fc">5.12.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.12.3/functions/fc">5.12.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.12.2/functions/fc">5.12.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.12.1/functions/fc">5.12.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.12.0/functions/fc">5.12.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.10.1/functions/fc">5.10.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.10.0/functions/fc">5.10.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.9/functions/fc">5.8.9</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.8/functions/fc">5.8.8</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.7/functions/fc">5.8.7</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.6/functions/fc">5.8.6</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.5/functions/fc">5.8.5</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.4/functions/fc">5.8.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.3/functions/fc">5.8.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.2/functions/fc">5.8.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.1/functions/fc">5.8.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.8.0/functions/fc">5.8.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.6.2/functions/fc">5.6.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.6.1/functions/fc">5.6.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.6.0/functions/fc">5.6.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.005_04/functions/fc">5.005_04</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.005_03/functions/fc">5.005_03</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.005_02/functions/fc">5.005_02</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.005_01/functions/fc">5.005_01</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.005/functions/fc">5.005</a>
        </div>
      </li>
      <li class="nav-item dropdown text-nowrap">
        <a class="nav-link dropdown-toggle" href="fc.html#" id="dropdownlink-dev" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Dev</a>
        <div class="dropdown-menu" aria-labelledby="dropdownlink-dev">
          <a class="dropdown-item" href="https://perldoc.perl.org/blead/functions/fc">blead</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.39.6/functions/fc">5.39.6</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.39.5/functions/fc">5.39.5</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.39.4/functions/fc">5.39.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.39.3/functions/fc">5.39.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.39.2/functions/fc">5.39.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.39.1/functions/fc">5.39.1</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.38.0-RC2/functions/fc">5.38.0-RC2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.38.0-RC1/functions/fc">5.38.0-RC1</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.11/functions/fc">5.37.11</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.10/functions/fc">5.37.10</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.9/functions/fc">5.37.9</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.8/functions/fc">5.37.8</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.7/functions/fc">5.37.7</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.6/functions/fc">5.37.6</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.5/functions/fc">5.37.5</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.4/functions/fc">5.37.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.3/functions/fc">5.37.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.2/functions/fc">5.37.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.1/functions/fc">5.37.1</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.37.0/functions/fc">5.37.0</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.11/functions/fc">5.35.11</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.10/functions/fc">5.35.10</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.9/functions/fc">5.35.9</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.8/functions/fc">5.35.8</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.7/functions/fc">5.35.7</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.6/functions/fc">5.35.6</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.5/functions/fc">5.35.5</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.4/functions/fc">5.35.4</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.3/functions/fc">5.35.3</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.2/functions/fc">5.35.2</a>
          <a class="dropdown-item" href="https://perldoc.perl.org/5.35.1/functions/fc">5.35.1</a>
          <a class="dropdown-item active" href="fc.html">5.35.0</a>
        </div>
      </li>
      <li class="nav-item dropdown text-nowrap">
        <a class="nav-link dropdown-toggle" href="fc.html#" id="dropdownlink-nav" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Documentation</a>
        <div class="dropdown-menu" aria-labelledby="dropdownlink-nav">
          <a class="dropdown-item" href="../perl.html">Perl</a>
          <a class="dropdown-item" href="../perlintro.html">Intro</a>
          <a class="dropdown-item" href="../perl.html#Tutorials">Tutorials</a>
          <a class="dropdown-item" href="../perlfaq.html">FAQs</a>
          <a class="dropdown-item" href="../perl.html#Reference-Manual">Reference</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="../perlop.html">Operators</a>
          <a class="dropdown-item" href="../functions.html">Functions</a>
          <a class="dropdown-item" href="../variables.html">Variables</a>
          <a class="dropdown-item" href="../modules.html">Modules</a>
          <a class="dropdown-item" href="../perlutil.html">Utilities</a>
          <div class="dropdown-divider"></div>
          <a class="dropdown-item" href="../perlcommunity.html">Community</a>
          <a class="dropdown-item" href="../perlhist.html">History</a>
        </div>
      </li>
    </ul>
    <ul class="navbar-nav">
      <script>
        function set_expand (expand) {
          var perldocdiv = document.getElementById('perldocdiv');
          var width = window.getComputedStyle(perldocdiv).getPropertyValue('max-width');
          var expanded = (width == '' || width == 'none') ? true : false;
          if (expand === null) {
            expand = !expanded;
          }
          if ((expand && !expanded) || (!expand && expanded)) {
            perldocdiv.style.setProperty('max-width', expand ? 'none' : '960px');
            var button_classlist = document.getElementById('content-expand-button').classList;
            if (expand) {
              button_classlist.add('btn-light');
              button_classlist.remove('btn-outline-light');
            } else {
              button_classlist.add('btn-outline-light');
              button_classlist.remove('btn-light');
            }
          }
          return expand;
        }
        function toggle_expand () {
          var expand = set_expand(null);
          document.cookie = 'perldoc_expand=' + (expand ? 1 : 0) + '; path=/; expires=Tue, 19 Jan 2038 03:14:07 UTC';
        }
        function read_expand () {
          return document.cookie.split(';').some(function (item) { return item.indexOf('perldoc_expand=1') >= 0 });
        }
        if (document.readyState === 'loading') {
          document.addEventListener('DOMContentLoaded', function () {
            if (read_expand()) {
              set_expand(true);
            }
          });
        } else if (read_expand()) {
          set_expand(true);
        }
      </script>
      <button id="content-expand-button" type="button" class="btn btn-outline-light d-none d-lg-inline-block mr-2" onclick="toggle_expand()">Expand</button>
    <ul>
    <form class="form-inline" method="get" action="https://perldoc.perl.org/5.35.0/search">
      <input class="form-control mr-3" type="search" name="q" placeholder="Search" aria-label="Search">
    </form>
  </div>
</nav>

    <div id="wrapperlicious" class="container-fluid">
      <div id="perldocdiv">
        <div id="links">
          <a href="../functions.html">functions</a>
            / <a href="fc.html">fc</a>
          <div id="more">
            (<a href="fc.txt">source</a>,
            <a href="CORE.html#fc-EXPR">CPAN</a>)
          </div>
        </div>
        <div class="leading-notice">
          You are viewing the version of this documentation from Perl 5.35.0.
            This is a development version of Perl.
        </div>
      <dl>

<dt id="fc-EXPR"><a class="permalink" href="fc.html#fc-EXPR">#</a><a id="fc1"></a>fc EXPR     </dt>
<dd>

</dd>
<dt id="fc"><a class="permalink" href="fc.html#fc">#</a>fc</dt>
<dd>

<p>Returns the casefolded version of EXPR. This is the internal function implementing the <code>\F</code> escape in double-quoted strings.</p>

<p>Casefolding is the process of mapping strings to a form where case differences are erased; comparing two strings in their casefolded form is effectively a way of asking if two strings are equal, regardless of case.</p>

<p>Roughly, if you ever found yourself writing this</p>

<pre><code>lc($this) eq lc($that)    # Wrong!
    # or
uc($this) eq uc($that)    # Also wrong!
    # or
$this =~ /^\Q$that\E\z/i  # Right!</code></pre>

<p>Now you can write</p>

<pre><code>fc($this) eq fc($that)</code></pre>

<p>And get the correct results.</p>

<p>Perl only implements the full form of casefolding, but you can access the simple folds using <a href="../Unicode::UCD.html#casefold%28%29">&quot;<b>casefold()</b>&quot; in Unicode::UCD</a> and <a href="../Unicode::UCD.html#prop_invmap%28%29">&quot;<b>prop_invmap()</b>&quot; in Unicode::UCD</a>. For further information on casefolding, refer to the Unicode Standard, specifically sections 3.13 <code>Default Case Operations</code>, 4.2 <code>Case-Normative</code>, and 5.18 <code>Case Mappings</code>, available at <a href="https://www.unicode.org/versions/latest/">https://www.unicode.org/versions/latest/</a>, as well as the Case Charts available at <a href="https://www.unicode.org/charts/case/">https://www.unicode.org/charts/case/</a>.</p>

<p>If EXPR is omitted, uses <a href="../perlvar.html#%24_"><code>$_</code></a>.</p>

<p>This function behaves the same way under various pragmas, such as within <a href="../feature.html#The-%27unicode_strings%27-feature"><span style="white-space: nowrap;"><code>&quot;use feature &#39;unicode_strings&quot;</code></span></a>, as <a href="lc.html"><code>lc</code></a> does, with the single exception of <a href="fc.html"><code>fc</code></a> of <i>LATIN CAPITAL LETTER SHARP S</i> (U+1E9E) within the scope of <a href="../locale.html"><span style="white-space: nowrap;"><code>use locale</code></span></a>. The foldcase of this character would normally be <code>&quot;ss&quot;</code>, but as explained in the <a href="lc.html"><code>lc</code></a> section, case changes that cross the 255/256 boundary are problematic under locales, and are hence prohibited. Therefore, this function under locale returns instead the string <code>&quot;\x{17F}\x{17F}&quot;</code>, which is the <i>LATIN SMALL LETTER LONG S</i>. Since that character itself folds to <code>&quot;s&quot;</code>, the string of two of them together should be equivalent to a single U+1E9E when foldcased.</p>

<p>While the Unicode Standard defines two additional forms of casefolding, one for Turkic languages and one that never maps one character into multiple characters, these are not provided by the Perl core. However, the CPAN module <a href="../Unicode::Casing.html"><code>Unicode::Casing</code></a> may be used to provide an implementation.</p>

<p><a href="fc.html"><code>fc</code></a> is available only if the <a href="../feature.html#The-%27fc%27-feature"><code>&quot;fc&quot;</code> feature</a> is enabled or if it is prefixed with <code>CORE::</code>. The <a href="../feature.html#The-%27fc%27-feature"><code>&quot;fc&quot;</code> feature</a> is enabled automatically with a <code>use v5.16</code> (or higher) declaration in the current scope.</p>

</dd>
</dl>


      </div>
      <div id="footer">
        <p>Perldoc Browser is maintained by Dan Book (<a href="https://metacpan.org/author/DBOOK">DBOOK</a>). Please contact him via the <a href="https://github.com/Grinnz/perldoc-browser/issues">GitHub issue tracker</a> or <a href="mailto:dbook@cpan.org">email</a> regarding any issues with the site itself, search, or rendering of documentation.</p>

<p>The Perl documentation is maintained by the Perl 5 Porters in the development of Perl. Please contact them via the <a href="https://github.com/Perl/perl5/issues">Perl issue tracker</a>, the <a href="https://lists.perl.org/list/perl5-porters.html">mailing list</a>, or <a href="https://kiwiirc.com/client/irc.perl.org/p5p">IRC</a> to report any issues with the contents or format of the documentation.</p>


      </div>
    </div>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.slim.min.js" integrity="sha512-/DXTXr6nQodMUiq+IUJYCt2PPOUjrHJ9wFrqpJ3XkgPNOZVfMok7cRw6CSxyCQxXn6ozlESsSh1/sMCTF1rL/g==" crossorigin="anonymous"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.1/umd/popper.min.js" integrity="sha512-ubuT8Z88WxezgSqf3RLuNi5lmjstiJcyezx34yIU2gAHonIi27Na7atqzUZCOoY4CExaoFumzOsFQ2Ch+I/HCw==" crossorigin="anonymous"></script>
    <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/js/bootstrap.min.js" integrity="sha384-B4gt1jrGC7Jh4AgTPSdUtOBvfO8shuf57BaghqFfPlYxofvL8/KUEfYiJOMMV+rV" crossorigin="anonymous"></script>
    <script src="../../highlight.pack.js"></script>
    <script>hljs.highlightAll();</script>
  </body>
</html>
